The present invention relates to an electrostatic air filter for removing from the air (or any other gas) relatively small particles.
In the past, a variety of dust collecting devices have been used to remove dust particles, mist, smoke particles and the like from gaseous material and particularly from air (hereinafter collectively referred to as "air"). In the more recent past, such dust collectors were constructed in the form of electrostatic air filters. They have the advantage of being relatively easy to maintain, similar in many respects to the theretofore more common mechanical filters. In addition, such filters exhibit the improved efficiency for collecting fine particles which is common to electrostatic precipitators.
Generally speaking, such electrostatic air filters are defined by two distinct sections. A first, upstream section ionizes the dust particles by flowing the air past a pair of electrodes. A corona discharge between the electrodes electrically charges the particles. Downstream of the ionizing section is a dust collecting filter which causes the removal of the charged dust particles from the air streaming past it. In addition, such filters may include a particle coagulator which coagulates charged fine particles to a larger size to facilitate the subsequent collection of the dust by the filter.
Typically, the filters had filter bodies constructed of glass, asbestos, natural or synthetic fibers such as cellulose or nylon, resin, grain material such as allumina or diatomaceous earth and the like. In order to effectively filter the dust from the air stream prior art filter bodies had to be constructed relatively dense and/or thick in the direction of air flow to assure that the particles impinge on the filter body. Only then would the filter remove the particle from the air stream. Thus, it was necessary to construct the filter of multiple, finely divided and closely adjacent strands, fibers, etc. to interrupt the laminar air flow and entrap the particles before they left the filter. This, in turn, increased the filter's flow resistance and thereby decreased its overall capacity. This drawback becomes more serious with an increase in the amount of filtered out material adhering to the filter element which in time could effectively clog it. In addition, this construction rendered prior art filters relatively difficult to maintain.